Carbon Nanotubes Research Articles

Utility of Gold/Multiwalled Carbon Nanocomposite for Electrochemical Determination of Omarigliptin in Tablets and Human Plasma

Abstract An innovative voltammetric sensor was developed to estimate omarigliptin, a novel long-acting anti-diabetic drug. The sensor utilized a carbon paste electrode enhanced with a nanocomposite of carbon nanotubes and electrodeposited gold nanoparticles. The modified electrode was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The modification significantly improved the electrode's sensitivity and electrochemical efficiency and decreased its electron transfer resistance. The surface area of the modified electrode increased by about 2.8-fold compared to the bare electrode. Omarigliptin's oxidation behavior on the modified electrode was pH-dependent and irreversible, resulting in a peak current 4 times higher than the unmodified electrode. The modified electrode revealed good reproducibility, reusability, and stability. It allows for sensitive voltammetric analysis of omarigliptin over a linear range of 0.4–27 µM (LOD=0.12 µM) and good applicability in tablets and plasma. The recovery percentages are 98.47–101.27% in tablets and 95.86–105.02% in plasma. The modified electrode exhibits good selectivity towards OMR without interference from tablet excipients, endogenous plasma components, and co-administered drugs. The comparison with the reported methods reveals the superiority of the proposed method in terms of sensitivity, selectivity, applicability, and eco-friendliness. Finally, the proposed method demonstrates excellent environmental profiles based on recent assessment metrics.

Chemi-Impeditive Sensing Platform Based on Single-Walled Carbon Nanotubes.

Chemical sensing methodology based on electrochemical impedance spectroscopy (EIS) targeting analytes in aqueous samples on functionalized single-walled carbon nanotube (SWCNT) is reported. The SWCNT in contact with electrolyte shows unique impedance spectra that cannot be analyzed with classical equivalent circuit models. Inspired by the charge transport property of mixed ionic-electronic conductors, we propose an equivalent circuit based on transmission line model (TLM), by which the impedance of the CNT-electrolyte system can be analyzed to track down all the equivalent circuit parameters. By combining multiple pieces of information, which are technically immeasurable with conventional chemiresistive or chemicapacitive techniques, several analyte species responding to the sensor can be differentiated from each other. We demonstrate the "chemi-impeditive" concept on chemically modified SWCNTs for detecting perfluoroalkyl substances (PFAS) in aqueous solutions. The EIS coupled with a fluorination chemistry on SWCNT surface provides unique changes in equivalent circuit components for each PFAS, i.e., changes in CNT and solution resistances, as well as interfacial CNT-solution capacitance, through which perfluorooctanesulfonic acid, perfluorooctanoic acid, hexafluoropropylene oxide dimer acid, and perfluorobutanesulfonic acid are detected in a discriminative manner. The new impedimetric method opens up new vistas in chemical sensing in that the EIS analysis provides an additional dimension of information beyond the single resistance or capacitance typically measured by many conventional types of sensors.

Thermo-electric Characterization of Hydroxyapatite/ Multi-walled Carbon Nanotube Reinforced Polyetheretherketone Polymer Composites

Thermo-electric Characterization of Hydroxyapatite/ Multi-walled Carbon Nanotube Reinforced Polyetheretherketone Polymer Composites

Sonochemical Synthesis of Potassium-Intercalated Carbon Allotropes: Bulk Formation at Ambient Room Temperature.

Intercalation can be used to alter the electronic properties of graphitic materials. Intercalation is, however, a notoriously brute-force process typically carried out at a high temperature in an inert environment for an extended period. As an exception to this, a simple sonication-assisted intercalation of potassium into graphite at ambient room temperature (RT) has been reported. Here we extend this approach to intercalation of potassium into other carbon allotropes, including planar graphene nanoplatelets (GNPs) and curved graphitic tubes and shells, such as multiwalled carbon nanotubes (MWCNTs) and nanodiamond-derived carbon nano-onions (NCNOs). We report the rapid room-temperature sonication-assisted potassium metal intercalation of GNPs, MWCNTs, and NCNOs. Powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and electron dispersive X-ray spectroscopy (EDS) were used to visualize the location of potassium in the intercalated products.

Effect of nickel catalyst thickness on growth of carbon nanotubes on glass nonwoven mat using thermal chemical vapor deposition method

This study aimed to explore how varying the thickness of nickel catalyst affects the synthesis of carbon nanotubes on glass mats using the thermal chemical vapor deposition (TCVD) method. Nickel served as the catalyst, with acetylene as the hydrocarbon source and argon as the carrier gas. Initially, different thicknesses of nickel catalyst were applied to the glass mat via plasma-enhanced chemical vapor deposition (PECVD). Subsequently, these samples underwent TCVD plasma treatment. Electrical resistance measurements were conducted, and scanning electron microscopy (SEM), Raman spectroscopy, and transmission electron microscopy (TEM) were employed to analyze the presence, surface morphology, and quality of the nanotubes. The research revealed that the thickness of the nickel catalyst significantly influences the nanotube synthesis process on glass mat substrates. An optimal thickness of nickel catalyst yielded a glass mat with an electrical resistance of 2 Ω per unit area post-TCVD treatment.

Adenosine-Derivative Functionalized Carbon Nanotubes Considered as Catalysts for Vanadium Flow Batteries

Adenosine-Derivative Functionalized Carbon Nanotubes Considered as Catalysts for Vanadium Flow Batteries

High‐Performance Alkaline Battery‐Supercapacitor Hybrid Based on Bimetallic Phosphide/Phosphate

AbstractTransition metal‐based materials explored for energy storage applications viz. batteries, supercapacitors and more recently battery‐supercapacitor hybrids (BSHs) abundantly involve Co‐based materials. However, the supply chain issues and low electronic conductivity force us to look for alternative options. In this regard, Co‐free binary metal phosphide/phosphate consisting of Ni and V metal (NiVP/Pi) microspheres as the positive electrode of BSH which shows a high specific capacity of 502 C g−1 (1004 F g−1) at 2 mV s−1 while retaining a high specific capacity of 214 C g−1 (428 F g−1) at 12 A g−1 is reported. The high electronic conductivity of binary metal phosphide in NiVP/Pi electrode and the rich electrochemical active sites due to Ni and V metal centres results in exciting performance. More interestingly, the hybrid device is successfully developed by employing NiVP/Pi as the positive electrode and carbon nanotubes (CNTs) as the negative electrode. The hybrid device (NiVP/Pi//CNT) is able to achieve a maximum energy density of 22.17 Wh kg−1 and a power density of 5 kW kg−1 with 91.7% capacitance retention after 7500 continuous galvanostatic charge–discharge cycles.

Optimizing Fe-N-C Electrocatalysts for PEMFCs: Influence of Constituents and Pyrolysis on Properties and Performance

Proton exchange membrane fuel cells (PEMFCs) are promising alternative technologies with applications in stationary power systems, vehicles, and portable electronics due to their low temperature operation, fast start-up, and environmental advantages. However, the high cost of platinum-based catalysts, in particular for the oxygen reduction reaction (ORR) of the cathode side, prevents their widespread incorporation. Fe-N-C electrocatalysts have emerged as viable alternatives to platinum. In this study, different precursor components were investigated for the way that they affect the pyrolysis process, which is crucial for tailoring the final catalyst properties. In particular, carbon allotropes such as carbon Vulcan, Ketjenblack, and carbon nanotubes were selected for their unique structures and properties. In addition, various sources of iron (FeCl2, FeCl3, and K[Fe(SCN)4]) were evaluated. The influence of the pyrolysis atmosphere on the resulting Fe-N-C catalyst structures was also assessed. Through an integrated structure and surface chemistry analyses, as well as electrochemical tests with rotating disk electrode experiments in acidic media, the ORR performance and stability of these catalysts were defined. By examining the relationships between carbon sources and iron precursors, this research provides valuable information for the optimization of Fe-N-C catalysts in fuel cell applications.

Mechanical and Tribological Properties of Carbon Fiber Reinforced POM Composite Filled With Maleamidic Acid Treated Carbon Nanotube

ABSTRACTIn order to attain improved mechanical properties of the carbon fiber (CF) reinforced polyoxymethylene (POM) composite, maleamidic acid treated carbon nanotube (CNT) was deposited on carbon fiber. The mechanical properties of composites have been investigated. The tensile strength values of the treated CF/POM composites at all CNT mixing ratios are found to be higher than that of untreated one. The surface morphologies of the fractured surfaces of the composites were recorded using scanning electron microscopy (SEM) to gain information about the fiber–matrix interfacial adhesion in the composites. The friction coefficient of all the CF/POM/CNT composites decrease as the load increases from 10 to 20 N under the same sliding speed of 1000 r/min. XPS results showed that the formation of C–O, C=O, and O–C=O based species give rise to chemical bonds of the CF and the POM.

Suppression of Pt Nanocluster Aggregation and Enhanced Oxygen Reduction Activity by Heteroatom Doping of Carbon Nanotubes

Suppression of Pt Nanocluster Aggregation and Enhanced Oxygen Reduction Activity by Heteroatom Doping of Carbon Nanotubes

Differentiation of adsorption and degradation in steroid hormone micropollutants removal using electrochemical carbon nanotube membrane

The growing concern over micropollutants in aquatic ecosystems motivates the development of electrochemical membrane reactors (EMRs) as a sustainable water treatment solution. Nevertheless, the intricate interplay among adsorption/desorption, electrochemical reactions, and byproduct formation within EMR complicates the understanding of their mechanisms. Herein, the degradation of micropollutants using an EMR equipped with carbon nanotube membrane are investigated, employing isotope-labeled steroid hormone micropollutant. The integration of high-performance liquid chromatography with a flow scintillator analyzer and liquid scintillation counting techniques allows to differentiate hormone removal by concurrent adsorption and degradation. Pre-adsorption of hormone is found not to limit its subsequent degradation, attributed to the rapid adsorption kinetics and effective mass transfer of EMR. This analytical approach facilitates determining the limiting factors affecting the hormone degradation under variable conditions. Increasing the voltage from 0.6 to 1.2 V causes the degradation dynamics to transition from being controlled by electron transfer rates to an adsorption-rate-limited regime. These findings unravels some underlying mechanisms of EMR, providing valuable insights for designing electrochemical strategies for micropollutant control.

Energy-efficient design and CNFET implementation of GDI-based ternary prefix adders

Abstract Ternary adders have produced more benefits compared to binary adders i.e., the ternary adder occupies less amount of area as well as produces less interconnect complexity. However, the CMOS implementation of the ternary adders failed to perform the process when the channel length was taken as 32 nm. At 32 nm technology, the CMOS transistors exhibit undesired effects such as Short Channel Effects (SCEs), mobility degradation, high leakage current, etc. Multi-gate devices are preferred to overcome these issues. Carbon Nano-tube Field Effect Transistors (CNFETs) are one of the technologies to work efficiently when the channel length is 32 nm. In this paper, CNFET-based ternary prefix adders are designed. Power consumption is the most critical requirement for the VLSI system, as it enhances energy efficiency and reduces heat dissipation. One way to achieve this power reduction is by minimizing the number of transistors employed in the adder circuits. This study employed a reduction technique known as Gate Diffusion Input (GDI) logic included in the proposed prefix adder design. The overall experimental investigation is done with the help of the HSPICE supporting platform. The proposed adder improved by reducing the power by up to 83%, energy by up to 83%, current by up to 78%, and delay by up to 96%. Finally, the Power Delay product (PDP) was also reduced by 84% compared to existing ternary adders. The proposed design proves to be highly effective in implementing the neuron structure, with the corresponding parameters thoroughly analysed and well-documented in this study.

Dispersion and Stability Behaviour of Graphene and MWCNT Based Nano-Lubricant for Vapour Compression Refrigeration (VCR) System

Incorporating nanoparticles into oil compressors marks a significant advancement in scientific research. It has been widely demonstrated that the inclusion of nanoparticles can markedly improve the system's efficiency by reducing energy consumption, decreasing evaporator temperatures, and increasing condenser temperatures. Nanoparticles made of carbon, including those of metal, metal oxide, and metal hybrids, are particularly valued for their superior properties and are deemed to have considerable potential for achievements. This study focuses on examining the stability of graphene and multi-walled carbon nanotubes (MWCNT) in polyolester (POE) oil as a precursor to replacing conventional lubricating oil in refrigeration systems separately. Graphene nano-lubricants were tested at concentrations ranging from 0.1 to 0.3 g/L with the selected surfactant, cetyltrimethylammonium bromide (CTAB), in a 1:1 ratio, while MWCNT nano-lubricants were tested from 0.5 to 0.7 g/L. All samples were prepared using a two-step method that involved magnetic stirring at 1250 rpm for 45 minutes, followed by ultrasonication for 30 minutes. The samples underwent evaluation through three methods of observation. Initial visual observation was conducted immediately after production, then after a 24-hour settling period, and finally, after seven days, the three most optimal samples were identified. For MWCNT, an additional stability test was necessitated due to the high concentration levels, making it challenging to determine the three most stable concentrations. The UV-VIS spectrophotometer played a crucial role in analyzing the stability of the samples, providing data that enabled more precise results. The absorption peak at a wavelength of 294 nm reached its highest absorption value of 0.892 (a.u.) at a concentration of 0.2 g/L. In the case of MWCNT, after testing all samples, concentrations of 0.5, 0.55, and 0.65 g/L were identified as the best options based on peak absorption at different wavelengths, with their peaks at 4.87, 4.045, and 4.116 (a.u.), respectively. The Zeta Potential Analyzer confirmed the stability of these concentrations, indicating a moderate stability with values around -37.4 mV. This level of stability was also observed in MWCNT samples, with the three chosen concentrations showing excellent stability at 88.4, -84.9, and -137 mV, respectively. Among all tested nano-lubricant samples, those with concentrations of 0.2 g/L and 0.65 g/L for Graphene/CTAB/POE and MWCNT/POE, respectively, demonstrated the highest stability and optimum performance. This suggests that these concentrations have the potential to serve as replacements for POE oil in refrigeration systems.

Flexural and vibration behaviour of co-cured CFRP composite joints with MWCNT-modified adhesive

Among the diverse adhesive-bonded joining methods, the co-curing technique offers several advantages for fusing structural components. Co-curing technique effectively enhances specific strengths and ensures more equitable stress distribution. This research investigated the multi-walled carbon nanotubes (MWCNTs) incorporated with varying wt.% in carbon fibre-reinforced polymeric (CFRP) composite joints through co-cure bonding techniques. The effects of flexural and vibration behaviour in CFRP composite joints were evaluated using the three-point bending and free vibration tests. Experimental results revealed that the epoxy adhesive containing 0.5 wt.% nanofiller demonstrated the highest flexural strength and modulus. These values were significantly superior to pure epoxy adhesive, exhibiting increases of 270 and 120%, respectively. However, the 1.0 wt.% of nanofiller exhibited the maximum natural frequency under three vibration modes, which is 29, 17, and 14% higher than the pure epoxy adhesive. The statistical analysis of the results was examined using an ANOVA, ensuring the reliability of the findings. Optimisation and prediction were done with the Levenberg-Marquardt artificial neural network, further reinforcing the confidence in the outcomes. The overall coefficient (R) mean square error of 0.99844 is within the acceptable range, indicating that both outcomes are reliable and in agreement.

Conductive Biocomposite Made by Two-Photon Polymerization of Hydrogels Based on BSA and Carbon Nanotubes with Eosin-Y

Currently, tissue engineering technologies are promising for the restoration of damaged organs and tissues. For regeneration of electrically conductive tissues or neural interfaces, it is necessary to provide electrical conductivity for the transmission of electrophysiological signals. The developed biocomposite structures presented in this article possess such properties. Their composition includes bovine serum albumin (BSA), gelatin, eosin-Y and single-walled carbon nanotubes (SWCNTs). For the first time, a biocomposite structure was formed from the proposed hydrogel using a nanosecond laser, and a two-photon absorption cross section value of 580 GM was achieved. Increased viscosity over 3 mPa∙s and self-focusing with a nonlinear refractive index of 42 × 10−12 cm2/W make it possible to create a biocomposite structure over the entire specified area. The obtained electrical conductivity value was 19 mS∙cm−1, due to the formation of effective electrically conductive networks. For a biocomposite with a concentration of gelatin 3 wt. %, formed by low-energy near-IR pulses, the survival of Neuro 2A nerve tissue cells was confirmed. The obtained results are important for the creation of new tissue engineering structures and neural interfaces from a biopolymer hydrogel based on the organic dye eosin-Y and carbon nanotubes by two-photon polymerization.

Buckling analysis of single‐walled carbon nanotubes using the initial value method and approximate transfer matrix based on nonlocal elasticity theory

AbstractIn this study, a novel method is presented to analyze the buckling behavior of single‐walled carbon nanotubes (SWCNTs) using the initial value method (IVM) in conjunction with the approximate transfer matrix, within the framework of nonlocal elasticity theory. The study aims to accurately approximate critical buckling load parameters under various boundary conditions, without encountering high computational requirements. IVM enables the computation of displacements and stress resultants along the entire beam from given initial conditions. The approximate transfer matrix is employed to analyze system states at different points through successive integration of solutions, generating the principal matrix needed for IVM and ensuring systematic and precise results that optimize the accuracy of the analysis. A convergence study confirms the effectiveness and precision of the proposed method, revealing a decrease in the critical buckling load parameters as the nonlocal parameter increases, applicable across all boundary conditions studied (simply supported, clamped–clamped, clamped–simply supported, and clamped‐free). These results underscore the need to incorporate nonlocal effects for more accurate nanostructure mechanics predictions. The integration of IVM and the approximate transfer matrix provides a computationally efficient alternative to traditional numerical and semi‐analytical methods, aiding researchers and engineers working with SWCNTs and other nanomaterials.

Unique Triboelectric Nanogenerator Using Carbon Nanotube Composite Papers

A unique triboelectric nanogenerator (TENG) using carbon nanotube (CNT) composite papers is proposed in this work. CNT composite papers can be fabricated easily using a method based on the production of Japanese washi paper. To obtain and evaluate the proposed TENGs, several types of CNT composite papers and aluminum plates were prepared. As the CNT composite paper contained many paper fibers, it was expected to be negatively charged, and the aluminum plate was expected to be positively charged across the triboelectric series. Through various experiments, it was confirmed that CNT composite papers could be used as TENGs. In addition, it was found that when a CNT composite paper was used, it contributed to triboelectricity generation, and the contained CNTs efficiently transferred the generated charge to the electrodes. Furthermore, output voltages approaching a maximum RMS value of 300 mV could be obtained. The results of this study will aid in the practical application of paper-based TENGs in the near future.

High‐potential and Stable Bipolar Cathode for Rechargeable Batteries with Fast‐charging and Wide‐temperature Adaptability

Organic carbonyl compounds have been recognized as promising electrodes due to multiple active sites, abundant element resources and flexible structural designability, while their practical applications are still hindered by the easy solubility and low discharge potential. Herein, a novel bipolar polymer composite (TAC) was well‐designed by grafting p‐type triphenylamine units onto n‐type anthraquinone to form an extended π‐conjugated structure and in‐situ growing on carbon nanotubes, which was proved not only with higher discharge potential but also effectively suppress the dissolution issues. Moreover, TAC combined the advantages of different active sites and behaved a dual‐ion storage mechanism. Benefitting from the in‐situ polymerization process, TAC with tube‐type core‐shell structure exhibited enhanced electron transport and improved utilization of active sites, resulting in high capacity (193 mAh g‐1), outstanding rate performance (fast charging within 17 s), long‐term stability (a high capacity retention of 87% after 1000 cycles) and high mass loading (10 mg cm‐2). Additionally, TAC can well adapt to the temperature change, outputting a capacity of 72 mAh g‐1 at ‐60 °C and 165 mAh g‐1 at 80 °C. Such versatile polymer structure inspires the design of high performance organic materials for rechargeable batteries to satisfy high stability and wide temperature operations.

High-potential and Stable Bipolar Cathode for Rechargeable Batteries with Fast-charging and Wide-temperature Adaptability.

Organic carbonyl compounds have been recognized as promising electrodes due to multiple active sites, abundant element resources and flexible structural designability, while their practical applications are still hindered by the easy solubility and low discharge potential. Herein, a novel bipolar polymer composite (TAC) was well-designed by grafting p-type triphenylamine units onto n-type anthraquinone to form an extended π-conjugated structure and in-situ growing on carbon nanotubes, which was proved not only with higher discharge potential but also effectively suppress the dissolution issues. Moreover, TAC combined the advantages of different active sites and behaved a dual-ion storage mechanism. Benefitting from the in-situ polymerization process, TAC with tube-type core-shell structure exhibited enhanced electron transport and improved utilization of active sites, resulting in high capacity (193 mAh g-1), outstanding rate performance (fast charging within 17 s), long-term stability (a high capacity retention of 87% after 1000 cycles) and high mass loading (10 mg cm-2). Additionally, TAC can well adapt to the temperature change, outputting a capacity of 72 mAh g-1 at -60 °C and165 mAh g-1 at 80 °C. Such versatile polymer structure inspires the design of high performance organic materials for rechargeable batteries to satisfy high stability and wide temperature operations.

Synthesis of spherical LiFePO₄ microparticles with encapsulated carbon nanotubes for high-power lithium-ion batteries

Lithium ferrophosphate – LiFePO₄(LFP) – is one of the widely studied and used materials for lithium-ion batteries. However, one of the main drawbacks of LFP is its poor electrical conductivity. To address this issue, we propose an effective approach based on encapsulating carbon nanotubes within the volume of LFP particles in the volume of spherical LFP particles. Electrodes based on the obtained materials exhibit more aTₜᵣactive electrochemical characteristics than LFP obtained by the standard method: increased specific capacity (62 and 92 mAh g–1 at a current density of 20C for LFP and LFP/SWCNT, respectively), stability of cyclic characteristics (preservation of 98% capacity after 100 charge/discharge cycles for LFP/SWCNT and 96.5% for LFP), as well as reduced charge transfer resistance. Encapsulation of SWCNT into the structure of iron phosphate during deposition is an easy-to-implement approach to formation modified LFP-based cathodes with improved characteristics, which expands the possibilities of their practical application in high-power lithium-ion batteries.